Jet silencer



March l, 1960 G. B. TowLE ETAL 2,926,744

JET SILENCER Filed March 15, 1957 Arrow/vlag .ET SILENCER George B. Towle, Glastonbury, and Jack W. Davis, East Hartford, Coun., assignors to United Aircraft Corporation, East Hartford, Coun., a corporation of Delaware Application March 13, 1957, Serial No. 645,787

2 Claims. (Cl. 181-55) This invention relates to jet power plants and more particularly to silencing mechanisms for the exhaust nozzles of these power plants.

Itis an object of this invention to provide a silencer for a jet exhaust nozzle with the silencer comprising a cylindrical or tubular extension of the nozzle with the extension having a plurality of holes `or perforations there- 1n.

It is -a further object of this invention to provide a series of baffles which surround the extension and diverge in a downstream direction to prevent recirculation of the exhaust gases into the powerv plant and to prevent over heating of adjacentV structure'such as the engine, pylon support or wing.

A still further object of this invention is to provide baffles which are perforated but which have a relatively small open area for greatly reducing the noise which may be caused by pressure fluctuations building up along the wall of the deflectors. n

These and other objects of this invention will become readily apparent from the drawing in which:

Fig. l is a schematic showing of a turbine type power plant having a jet exhaust silencer according to this invention; `and Fig. 2 is an enlargement of the silencer mechanism of Fig. l.

Referring to Fig. 1, a turbine type jet power plant is generally indicated `at 10. The power plant includes a compressor section 12, a combustion section 14, a turbine section 16 land an exhaust nozzle 1S. The exhaust nozzle 18 terminates in an aft opening from which the hot gases areA emitted. The nozzle 18 has a silencer generally indicated at 20 attached to the aft end of the nozzle 18 by means of a suitable ange 22 and bolts 24.

As best seen in Fig. 2, the silencer 20 comprises anV upstream opening for receiving the exhaust gases from the exhaust nozzle 18.' The silencer 20 comprises a cylindrical or tubular member 3-2 which extends in an aft direction from the exhaust nozzle 18 and includes longitudinal extending walls having a plurality of holes or perforations therein. The aft or trailing end of the cylindrical member 32 terminates in a closure 36 which may also include a number of holes or perforations 38.

In order to norrn-ally prevent recirculation of exhaust gases into the power plant, a plurality of bales or deectors 40, 42, and 44 are provided. In the past these baflies had been made solid, and pressure fluctuations along the dellector created noise which reduced the effectiveness of the silencer. Solid or imperforate bales are shown in Vpatent application Serial No. 581,418, led April 30, 1956, by Tyler and-Towle. By having the bales or detlectors such as 40, 42, and 44 perforated with a relatively small opening area, not only is recirculation and overheating avoided but this will provide a substantially lower noise level. Depending upon the particular conditions, the perforated bailles should have an angle relative to the longitudinal axis of the silencer which in the range of 20 to 50'.

The baies 40, 4Z, and 44 have, angesSl), 52l and 54, respectively, which aresuitably attached Ato the tube 32 as by welding or rivets. The ilanges form the leading edges of the bales and the ange 52 is substantially aligned with the trailing edge of the baffle 40. The relationship of the leading edge of one bale to the trailing edge of the next upstream balile is a distance apart in the range 0 to .4l where l length ot lche sound suppressor tube 32 number of ba-les As a resul-t of this invention it is apparent that a highly efficient yet lightweight silencer mechanism has been provided which will reduce the noise level of jet engines by a marked degree.

Although only one embodiment of this invention has been illustrated and described herein, it will become readily apparent thatvarious changes and modifications may be made in the construction and arrangement of the various parts without departing from the scope of this novel concept.

What is desired by Letters Patent is:

l. In an exhaust nozzle for a jet exhaust, a tubular member extending aft of said exhaust nozzle and having a jet exhaust receiving opening adjacent its upstream end, said tubular member having longitudinallyV extending sido walls and a closure at its downstream end, said side walls and said closure being perforated to emit gases tothe free airstream, a plurality of perforated frusto-conica baies having inner and outer ends and extending radially from said tubular member and surrounding said member to detlect the emitted gases in a downstream direction, the

kperforations in said haiiles presenting a relatively `low open area, said baffles having ywalls which diverge in a downstream direction, said baliies having their outer ends free and located downstream of said inner ends, and mounting means for securing the inner ends of said bafes to said member which inner end abuts said member, each of said baffles having its downstream edge approximately aligned with the upstream end of the next adjacent downstream baiile along the longitudinal axis of said member.

2. In an'exhaust nozzle for a jet exhaust, a tubular member extending aft of said exhaust nozzle and having a jet exhaust receiving opening adjacent its upstream end, said tubular member having longitudinally extending side walls and a closure at its downstream end, said tubular member having a longitudinal axis, said side walls and said closure being perforated to emit gases to the free airstream transversely of the longitudinal axis of said member, a plurality of perforated frusto-conical b-ales having inner and outer ends land extending radially from said tubular member and surrounding said member to deflect the emitted gases inaI downstream direction, the perforations in said baiiies presenting a relatively low open area, said baiiles having walls which diverge in a downstream direction at an angle relative to the longi tudinal axis of said member which angle is in the range between 20 and 50, said baliles having their outer ends free and located downstream of said inner ends, and mounting means for securing the inner ends of said baffles to said memberwhich inner end abuts said member and comprises the upstream end of the baille, each of said baflles having its downstream edge vapproximately aligned with the upstream end of the next adjacent downstream baiile along the longitudinal axis of said member and the distance between said upstream and downstream edges and said adjacent baies being in the range of 0 to .4l where l lenatah of the tubular member number of baliles (References on following page) References Cited in the file of this Ypatent UNITED STATES PATENTS 546,538 i l787,860 Sharpe 1 Aprvf 1s, 1905 851912 -1,401,368 schweben nec. 27, 1921 5 Schultz Sept. 18, 1928 FOREIGN PATENTS Germany Mar. 15, 1932 France Sept. 25, 1939 

